Back to Volume
Paper: Kinematic Parameters of Local Disk Components Determined from a Geometrical-Statistical Method
Volume: 230, Galaxy Disks and Disk Galaxies
Page: 43
Authors: Alcobé, S.; Cubarsi, R.
Abstract: Most stars in the solar neighbourhood seem to belong to two main components of the galactic disk. In order to identify the mixture, a combined geometrical-statistical method has been developed. For computing the parameter values, a two-component local sample is drawn from a neighbour stars catalogue by using a non-informative filtering method. The density function is approximated with a superposition of two trivariate normal distributions. A set of projected residual velocity moments is used to determine the population covariance matrices, population mean velocities - especially the radial component- vertex deviation and mixture proportions. The method does not require any extra hypotheses such as those concerning to prior population parameters, restricted differential motions or stellar system symmetry. The deduced kinematic parameters lead to some conclusions, the most remarkable of them are: One component -corresponding to old disk stars- is compatible with dynamic models accepting axial symmetry and shows no vertex deviation. The other component -associated with young disk stars- shows no negligible vertex deviation and requires a point axial symmetry model in order to explain its kinematics. Moreover, a radial differential movement between both components is detected in addition to the old disk stars rotational lag.
Back to Volume